The present invention relates to electrostatic precipitators, and more particularly to an improved rapping system for such precipitators.
Electrostatic precipitators consist of a number of collecting electrodes which may be plates, or may be of other suitable configurations, with associated high-voltage or corona discharge electrodes to maintain a strong electric field which charges particles passing through it. The charged particles are attracted to the collecting electrodes which are grounded, or of opposite polarity to the high-voltage electrodes, so that the charged particles deposit on the collecting electrodes and are thus removed from the air or gas stream passing through the precipitator. The particulate matter thus removed accumulates on the collecting electrodes and may be allowed to fall off by gravity. In many cases, however, the deposited material builds up quite rapidly, or does not readily fall off, and must be positively removed by suitable means. This is often done by mechanically rapping or jarring the electrodes at regular intervals to knock off the accumulated deposits of particulate matter. Rotating or swinging hammers have been used for this purpose, as well as reciprocating hammers or other impact devices. The rotating or swinging hammers have usually been placed inside the precipitator casing and positioned to directly impact the collecting plates, preferably with horizontally-directed impacts in the plane of the plates and centrally of the plates or at the edges. This arrangement, however, makes it necessary to increase the size of the casing in order to accommodate the hammers, while the rapping mechanism is inaccessible for maintenance or adjustment during operation of the precipitator. It has also been proposed to place the rapping mechanism above the plates but this involves the problem of avoiding interference with the supports and electrical supply system of the high-voltage electrodes which extend between the collecting electrodes.